Where there’s smoke, there’s fire. But the same can’t always be said for a smoke alarm.

What does it mean when a smoke alarm goes off for no apparent reason? Well, as annoying as it is, it isn’t something you should ignore. There’s always a reason – it just isn’t always obvious.

Smoke alarms are an essential component of your home safety system, and if they’re not working right, they could throw a wrench in your emergency plans.

Here are some of the possible reasons why your smoke alarm would go off when there’s no fire:

Steam. Smoke alarms are triggered by dense moisture in the air, like the steam from a hot shower or boiling water on the stove. This is less common than false alarms caused by burning food (which is obvious enough not to include here), but it can happen. It means the device is working as intended. However, if this is a persistent problem, you’ll either have to move the device or cut down on the steam.

Strong chemical odors. Paint, cleaning supplies, and other strong chemicals can set off a smoke alarm. Store these items away from the device. It’s worth noting that if the odor is strong enough to set off the smoke detector, it probably isn’t good for your lungs, either – so take caution if this is the source of your problem.

Heavy dust. A normal volumes of dust that accumulates in the home shouldn’t set off the alarm, but heavy dust from remodeling or home renovations can settle on the sensor. To prevent future occurrences, you’ll have to take the device apart and clean any built-up dust. Once again, if the dust is thick enough to bother the smoke alarm, it’s going to bother your lungs as well!

Bugs. Though unlikely, it is possible for small bugs to crawl into the device and set it off. If you’ve searched high and low and can’t find what triggered the alarm, this could be your culprit. Carefully open the smoke detector and remove any creepy crawlies that have made the mistake of moving in.

High humidity. Like steam, the dense moisture of high humidity can trigger a smoke alarm. If it’s a particularly muggy day and the house isn’t well ventilated, humidity can cause the alarm to sound.

Low battery. Most smoke alarms are designed to make a chirping sound to indicate the battery is low. However, this is usually distinguishable from a full-blown alarm and easily fixed by replacing the batteries. Never ignore this sign of low battery.

A final note – fires don’t always show themselves right away. Your smoke alarm (if it’s functioning well) will almost always notice a fire before you do, including small electrical fires or other hidden flames that have yet to spread.

Even if you don’t see the fire yourself, you should never simply ignore the alarm. If it goes off at night, and there are no obvious reasons why, stay up for at least an hour to ensure there’s not really a fire.